1. Technical Field
The present disclosure relates to amplitude-shift-keying (ASK) radio frequency (RF) signal decoding technology, and more particularly, to an ASK RF signal decoding device capable of decoding the ASK RF signal by counting a divided signal during a non-pause section of a low frequency signal, which is included in an ASK RF signal, and a method thereof.
2. Discussion of the Related Art
An integrated circuit card, also known as a smart card is widely used to conduct electronic financial transactions such as paying bus or subway fares, as a credit card, as an ID card, for paying cash by a contact-less method, or as a storage medium storing a credit card number or personal information, etc.
The integrated circuit card (IC Card) may use for communicating a standard communication protocol of a contact-less proximity IC card named ISO/IEC 14443 standard, for example. Physical characteristics and a communications protocol (a wireless frequency power and a communication signal connection, an initialization and collision prevention, etc.) of a contact-less proximity IC card are defined in the ISO/IEC 14443 standard. The ISO/IEC 14443 standard defines two types of communication signal connection methods, i.e., A-type and B-type.
FIG. 1 illustrates an example of a RF signal for an A-type interface according to the ISO/IEC 14443 standard. When connected, an amplitude shift keying ASK 100% modulation method and a correction miller code communicates wirelessly within a range of wireless frequencies between a card reader and an IC card.
In addition, as a method of transmitting data from the IC card to the card reader, a Manchester code method and an On-Off key (OOK) method may be used.
Generally, a card used in a communication signal connection mode of ISO/IEC 14443 A-type receives and transmits every bit of data by generating timing in a certain interval from an ASK RF signal received from a card reader, and when data is transmitted from an IC card to a card reader, power transmitted from a card reader to the IC card is stably supplied. However, when data is transmitted from the card reader to the IC card, there is a pause section t2 in which power supplied from a card reader to the IC card may be interrupted as illustrated in FIG. 1.
That is, since there is a section in which power supplied from a card reader to the IC card is interrupted, an ASK RF signal output from the card reader may be distorted during decoding and a clock signal generated in the IC card may include a discontinuous section.
Therefore, when an IC card generates a receiving and transmitting synchronized clock signal by dividing a clock signal including a discontinuous section, it may be difficult to maintain the bit transmission rate of the ISO/IEC 14443 A-type standard.